Typewriter



5. BAUMANN Jan. 26, 1937.

TYPEWRITER Filed Feb. 26, 1955 In venzor':

B Bqun'nann,

Patented Jan. 26, 1937 mawmua Berthold Baumann, Nuremberg, Germany, as-

signor to Triumph-Werke Niirnberg A.-'G., Nuremberg, Germany Application February 26, 1935, Serial No. 8,406

Germany 3 Claims.

Devices for the silent return of the carriage in typewriters are known in various constructional forms, in which spring-loaded pawls are used, which engage in ratchet wheels and are 5 brought into and out of operation by friction members or similar arrangements. In these carriage returning devices there is'always the disadvantage, that the left-hand margin becomes irregular, because the detents or the loose pawl 10 frequently do not engage with certainty at the right moment, so that the first letter of the line is typed in the second or third place.

The invention adopts an entirely new way for the silent return of the paper carriage, making use of the known free-wheel arrangement in which small rollers r balls make or break the connection between the ratchet escapement wheel and the toothed wheel of the carriage. This makes the device for the return motion of the carriage independent of springs, which become fatigued in course of time, and of friction, so that the disadvantage of an irregular margin, which occurs with the known devices, is also diminished.

The invention consists in the employment of a free-wheel arrangement provided in the carriage escapement mechanism, such that on the shaft of the shifting mechanism a driving wheel having trough-like recesses is mounted loosely, 3 the trough surfaces of which control the rollers or balls disposed between the driving wheel and a cage fixed to the escapement wheel positively in such a manner that, during the forward motion of the carriage, the rollers or balls couple the driving wheel with the escapement wheel and, during the return motion of the carriage, are forced into inclined slots in the cage. The number of troughs is equal to the number of ratchet teeth and the pitch of the troughs and 40 of the ratchet teeth corresponds to the spacing of the letters, so that for each coupling operation there corresponds to a definite position of the escapement wheel a definite position of the driving wheel and of the rollers or balls dropping into the troughs.

As the rollers are very light, the motionof the rollers as they drop into the troughs of the driving wheel or into the inclined slots of the cage during typing or their displacement into these slots and their dropping back into the troughs during the return motion of the carriage is inaudible.

For ensuring coupling and uncoupling of the escapement wheel in the case of small type as well, the inclined slots in the cage are in this March 5, 1934 case made not equidistant from one another, but each second inclined slot is displaced with respect to the trough pitch by a distance equal to half the pitch, so that coupling between the driving wheel and the ratchet wheel takes place with a rotation through half a trough pitch.

A constructional example of the invention is illustrated in the accompanying drawing in which Fig. 1 is,a longitudinal section through the device,

Fig. 2 an end view of the uncovered cage with escapement wheel and driving wheel, the parts being in the coupling position, that is during typing,

Fig. 3 an end view of the parts shown in Fig. 2 in the uncoupled position, that is during the return motion of the carriage,

Fig. 4 an end view of the parts similar to Fig.

2 with a cage in which, however, each second inclined slot is displaced by half the pitch with respect to the trough pitch and Fig. 5 a portion of the driving wheel to an enlarged scale.

On the shaft I of the ratchet mechanism is mounted loosely the hollow shaft 3, known per se, which supports the feed pinion 2 gearing with the rack of the carriage and at the inner end of which is the part 4 of the claw coupling, while the outer end carries a compression spring 5. 80 The escapement wheel 6 is fixed on the shaft I and is rigidly connected to a cage 1 having a plurality, for instance 6, of inclined recesses or inclined slots, w, b, c, d, e, 1. Within the cage 1 is loosely mounted on the shaft I the driving wheel 8, the periphery of which has a number 01' troughs 9 corresponding to the number of ratchet teeth, each of which troughs has a steep and a. flat curved part 9a and 9b (Fig. 5). The 0 coupling members between the cage 1 and the 7 driving wheel 8 consist of small rollers or balls, which fit in the troughs 9. The driving wheel 8 is provided with a claw coupling part II, in which engages the claw coupling part 4 of the hollow shaft 3 under the pressure of the spring 5.

The number of inclined slots is optional, being preferably such that several rollers simultaneously take part in the coupling action.

During the usual typing motion the escapement wheel 6 is advanced under the influence of the carriage-driving spring for pulling the carriage step by step in the direction of the arrow A. The parts will then occupy the position shown in Figs.

1 and 2. From the feed pinion 2 the driving wh 8 is turned through the claw coupling 4, I l in the direction of the arrow A and for instance three rollers l0 establish at the inclined surfaces of the slots b, a, f the coupling between the driving wheel 8 and the cage 1 and consequently the escapement wheel 6. The other three rollers 10 rest, owing to their weight in the inclined slots e, d, c and therefore do not take part in the coupling action. On the escapement wheel continuing to turn, first of all the roller l0 opposite the inclined slot 1 will drop back into the latter, while the roller III of the inclined slot 0 drops out of the latter, enters the associated trough and acts as a coupling member. The steep surfaces 9a of the troughs prevent the coupling rollers being forced back into their inclined slots.

On pushing back the carriage, the feed pinion 2 turns in the direction indicated by the arrow B and consequently, owing to the action of the claw coupling 4, H, the driving wheel 8 in the same sense (Fig. 3) At the same time the rollers which were hitherto wedged in are pushed by means of the gently inclined surfaces 9b of the troughs into the inclined slots f, a, b, so that the driving wheel 8 can turn under the rollers. The forced-back rollers drop into the following troughs, but are immediately pushed by the surfaces 91) of these troughs back into their inclined slots. The rollers thus wander continuously to and fro in the slots; as however their weight and the friction are very slight, they cause no noise. The driving wheel 8 can therefore turn freely and the escapement wheel 6 remains stationary.

In the constructional form of the cage la in Fig. 4 the distances apart of the inclined slots a, b; c, d and e, f are smaller by half the trough pitch than the distances a, b; c, c! and e, fin Fig. 2. The rollers l0 couple for instance at the slots 1) and I, while the roller at the slot a rests on the point between two adjacent troughs. On turning the driving wheel 8 backwards, coupling does not only take place when at the end of the backward motion an entire trough pitch has been travelled through, but after passing through one half of a trough pitch, for the roller in the slot a is ready to drop in and, after a rotation through a half pitch, drops into the adjacent trough.

This displacement with respect to one another of the slots by half the pitch of the troughs has the object of enabling one and the same driving wheel to be used for typewriters in which the size of the letter spacing movement is 2.38 mm. apart and for those in which the size of the letter spacing movement is 1.44 mm. apart. If the trough pitch were to be adapted to the small type spacing of 1.44 mm., the trough pitch would be so small that it would no longer be polsible in practice to make the control surfaces 9b and 9a with their different inclinationsso as to obtain a reliable positive control of the rollers.

When the escapement wheel with cage, rollers and driving wheel is to be entirely disconnected from the feed pinion, the hollow shaft 3 may be pressed back in a known manner, causing the claw coupling 4, H to become disengaged. The carriage can then be pushed to and fro unhindered by hand.

In order to protect the cage, the rollers or balls and the driving wheel from dust, the cage 1 is enclosed in a dust-tight manner by a cap-like cover l2.

What I claim is:-

1. In a typewriter carriage escapement mechanism, the combination of a shaft, a ratchet escapement wheel on said shaft and a feed pinion on the shaft rotatable relatively to said escapement wheel, with a free wheel'drivlng connection between the escapement wheel and the feed pinion and comprising a cage fixed to the escapement wheel and having inclined slots therein spaced around its inner periphery, a driving wheel operatively connected to the feed pinion mounted on the shaft inside said cage, said driving wheel having a plurality of trough-like recesses therein spaced around its periphery equal to the number of teeth of the escapement wheel, and rolling members in said slots for establishing driving connection between the driving wheel and the cage, said rolling members being capable of protruding from the slots into engagement in the recesses in the driving wheel and the direction of inclination of the slots being such that in the forward movement of the carriage the driving wheel is coupled with the cage and in the backward movement of the carriage the driving wheel is uncoupled from the cage.

2. In a typewriter carriage escapement mechanism, the combination of a shaft, a ratchet escapement wheel on said shaft and a feed pinion on the shaft rotatable relatively to said escapement Wheel, with a free wheel driving connection between the escapement wheel and the feed pinion and comprising a cage fixed to the escapement wheel and having inclined slots therein spaced around its inner periphery, a driving wheel operatively connected to the feed pinion mounted on the shaft inside said cage, said driving wheel having a plurality of trough-like recesses therein spaced around its periphery equal to the number of teeth of the escapement wheel, and rollers in said slots for establishing driving connection between the driving wheel and the cage, said rollers being capable of protruding from the slots into engagement in the recesses in the driving wheel and the direction of inclination of the slots being such that in the forward movement of the carriage the driving wheel is coupled with the cage and in the backward movement of the carriage the driving wheel is uncoupled from the cage.

3. In a typewriter carriage escapement mechanism, the combination of a shaft, a ratchet escapement wheel on said shaft and a feed pinion on the shaft rotatable relatively to said escapement wheel, with a free wheel driving connection between the escapement wheel and the feed pinion and comprising a. cage fixed to the escapement wheel and having inclined slots therein spaced around its inner periphery, a driving wheel operatively connected to the feed pinion mounted on the shaft inside said cage, said driving wheel having a plurality of trough-like recesses therein spaced around its periphery equal to the number of teeth of the escapement wheel, the spacing between the slots in the cage differing from the spacing of the troughs in the driving wheel by one half the pitch of the troughs, and rolling members in said slots for establishing driving connection between the driving wheel and the cage, said rolling members being capable of protruding from the slots into engagement in the recesses in the driving wheel and the direction of inclination of the slots being such that in the forward movement of the carriage the driving wheel is coupled with the cage and in the backward movement of the carriage the driving wheel is uncoupled from the cage.

BERTHOLD BAUMANN. 

